Impairment of the CD8+ T cell response in lungs following infection with human respiratory syncytial virus is specific to the anatomical site rather than the virus, antigen, or route of infection

Abstract

Background: A subset of the virus-specific CD8+ cytotoxic T lymphocytes (CTL) isolated from the lungs of mice infected with human respiratory syncytial virus (RSV) is impaired in the ability to secrete interferon gamma (IFNgamma), a measure of functionality. It was suggested that the impairment specifically suppressed the host cellular immune response, a finding that could help explain the ability of RSV to re-infect throughout life.

Results: To determine whether this effect is dependent on the virus, the route of infection, or the type of infection (respiratory, disseminated, or localized dermal), we compared the CTL responses in mice following intranasal (IN) infection with RSV or influenza virus or IN or intradermal (ID) infection with vaccinia virus expressing an RSV CTL antigen. The impairment was observed in the lungs after IN infection with RSV, influenza or vaccinia virus, and after a localized ID infection with vaccinia virus. In contrast, we observed a much higher percentage of IFNgamma secreting CD8+ lymphocytes in the spleens of infected mice in every case.

Conclusion: The decreased functionality of CD8+ CTL is specific to the lungs and is not dependent on the specific virus, viral antigen, or route of infection.

Figure 1

Examples of primary data of flow cytometry analysis of tetramer/pentamer+CD8+ and IFNγ+CD8+ cells from the lungs and the spleens of individual mice. Mice were mock-infected or infected as indicated below the plots on days 0 and 28. The animals were sacrificed 8 days later (day 36) and lungs and spleens were collected. PMC and splenocytes were isolated and stained with MHC class I tetramer or pentamer complexes specific for an RSV or influenza virus epitope or stimulated in vitro with the epitope-specific peptide, stained for intracellular IFNγ and analyzed by flow cytometry. Percentages relative to total CD8+ cells are shown for various cell populations. The data are from the experiment shown in Table 1.

Figure 2

CD8+ cells secreting IFNγ as % of tetramer/pentamer+CD8+ cells. PMC or SMC were isolated from the lungs and the spleens, respectively, of mice on days 8 and 28 after the primary (A, B) or the secondary (C, D) infection, as indicated under the plots. The values were determined by dividing the numbers of IFNγ+CD8+ cells by the numbers of tetramer/pentamer+CD8+ cells and expressed as percentages. RSV and VV-M2-specific CD8+ T cells were analyzed using the RSV-specific tetramer, and the influenza virus-specific CD8+ T cells were analyzed using the influenza virus-specific pentamer. The data are from the experiment shown in Table 1. The values for the lungs and the spleens are shown by black and striped bars, respectively.